GB2036296A

GB2036296A - Gas turbine

Info

Publication number: GB2036296A
Application number: GB7937901A
Authority: GB
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1978-11-20
Filing date: 1979-11-01
Publication date: 1980-06-25
Also published as: DE2946393A1; GB2036296B; US4305255A; DE2946393C2; FR2441725B1; JPS5575537A; FR2441725A1

Description

c

SPECIFICATION Gas turbine engine

This invention relates to a gas turbine engine having a combustion system comprising an annular combustion chamber including first fuel injection nozzles fed with fuel for a tow power operating range, and second fuel injection ndzzles fed with fuel, along with said first nozzles, for a high power operating range of the engine.

Since the change from the low power to the 75 high power range has to be made while the engine is operating, it can be a difficulty to provide a system for controlling the priming of any fuel manifold leading to the second nozzles. Similarly, since such a manifold would have to be purged when changing from the high power to the low power range, it can be a difficulty to provide a system for controlling such purging. It is an object of this invention to alleviate or overcome this difficulty.

According to this invention there is provided a gas turbine engine having a combustion system comprising an annular combustion chamber, an annular array of pairs of radiaily spaced apart first and second nozzles, a fuel supply manifold having branch ducts leading to the respective pairs of nozzles, each branch duct being connected to the first nozzle of a respective pair directly and to the second nozzles of a respective pair through a shut off valve.

The provision of a said cut-off valve in respect of each of said manifold branch ducts substantially reduces the volume of any passage through which fuel has to pass when the second nozzles are to be supplied with fuel so that neither priming nor purging are necessary.

An example of a gas turbine engine having a combustion system according to this invention will now be described with reference to the accompanying drawings wherein Fig. 1 is a sectional elevation of the combustion chamber region of the engine.

gig. 2 is a section on the line 11-11 in Fig. 1.

Fig. 3 is an enJarged sectional detail of Fig. 1.

Referring to Fig. 1, an annular combustion chamber 10 receives air from a compressor 11 and fuel from a fuel supply manifold 12, and discharges combustion products through a turbine 12 connected to drive the compressor. The manifold feeds a number of fuel injectors 14 distributed around the annulus of the combustion 115 chamber. Each injector has a first orpilot nozzle and a second or main nozzle 16. In use fuel is injected into the combustion chamber through the pilot nozzle during a low speed range of the engine, say between idle and 30% of maximum thrust Above that range fuel is also injected through the main nozzle 16. The nozzles 15, 16 are supported by an elongate structure or housing 17 having an end 1 7A supported by a casing 1 OA surrounding the combustion chamber 10. The housing 17 extends from the casing 1 OA radially inwardly into the combustion chamber 10, the nozzle 16 being situated at the end 17B and the GB 2 036 296 A 1_ nozzle 15 being situated at a location intermediate between the ends 1 7A, 1 7B. Each housing 17 contains a passage 1 9A extending the full length of the housing and connected at the end 1 7B to a further passage 1913 leading directly to the nozzle 15. The passages 1 9A, 198 are parts of the branch duct 19. The nozzle 16 is connected to the passage 1 9A through the intermediary of a shut off valve 2 1.

The valve 21 has a closure member 22 connected by a stem 23 to one side of a diaphragm 24 contained in a chamber 25 at the end 1 7A of the housing. At the other side of the diaphragm, the chamber 25 is connected to a branch duct 26 of a pressure supply manifold 27.

The valve 21 is normally open by virtue of a bias of the diaphragm. When it is desired to close the valves 21 of the respective injectors 14, pressurized fuel is supplied from a continually operating pump 29 (Fig. 1) through a three-way control valve 30 to a supply duct 31 of the manifold 27.

The valve 21 is a lift valve arranged to directly control a port 18 leading into the nozzle 16. Thus, when the valve 21 is being opened, fuel is immediately available at the.main nozzle 16 and there is no need to prime any feed passage, e.g. a separate manifold feeding the nozzles 16, leading to the port 18. Correspondingly when the valve 21 is being closed, there is no such feed passage which needs to be purged to ensure a clean cut-off of the fuel.

The passage 19A surrounds the stem 23 as shown (Fig. 3) so that the relatively low temperature of the incoming fuel is available for cooling the stem 23 as well as the surrounding part of the housing 17.

The pump 29 is primarily intended for feeding a supply duct 32 to the manifold 12 and contains a throttle valve 33 for regulating the fuel supply to the nozzles 15, 16. The duct 3 1 is connected to the pump 29 at a point 3 1 A upstream of the valve 33. Since the valve 33 constitutes a flow restrictor, the pressure in the duct 31 and, on opening of the valve, the pressure in the manifold 27 must always be higher than the pressure in the manifold 12. Therefore, on opening of the valve 31 the pressure in the manifold 27 is sufficient to act on the diaphragm 24 in the sense of closing the valve 21.

Claims

1. Gas turbine engine having a combustion system comprising an annular combustion chamber, an annular array of pairs of radially spaced apart first and second nozzles, a fuel supply manifold having branch ducts leading to the respective pairs of nozzles, each branch duct being connected to the first nozzle of a respective pair directly and a shut-off valve being provided between each said branch duct and the respective said second nozzle.

2. Gas turbine engine according to claim 1 comprising in respect of each shut-off valve a fluid pressure actuator, and further comprising a 2 pressure supply manifold having branch ducts connected to the respective actuators for operation thereof by variation of pressure in said 25 pressure supply manifold, and a control valve provided in a fluid pressure supply duct to the latter manifold for varying said pressure.

3. A gas turbine engine, according to claim 2 comprising a fuel pump, a fuel supply duct connected between said pump and said fuel 1 c) supply manifold for the supply of fuel thereto, a flow restrictor in said fuel supply duct, said pressure supply duct being connected to said fuel supply duct at a point upstream of said restrictor 35 so that the pressure for operating said actuators is greater than the pressure in said fuel supply manifold, and wherein each said actuator is arranged to close said shut-off valve responsive to the pressure in said supply manifold and open said shut-off valve responsive to the pressure in the fuel supply manifold when said operating valve is operated to reduce the pressure in the pressure supply manifold to a level below that in the fuel GB 2 036 296 A supply manifold.

4. Gas turbine engine according to claim 1 comprising in respect of each said pair of nozzles an elongate structure having a supported and a free end, said first and second nozzles being supported respectively at a location intermediate between said ends and a location at said free end, said branch duct of the fuel supply manifold extending longitudinally through said structure to said second nozzle and from there to said first nozzle, the shut-off valve being provided between the duct and the second nozzle at said free end.

5. Gas turbine engine according to claim 4 wherein said actuator comprises a pressureresponsive member situated at said supported end and a rod extending through said duct between the pressure-responsive member and said shut-off valve for the operation thereof by said actuator.

6. Gas turbine engine having a combustion system substantially as described herein with reference to the accompanying drawings.

P6nted ftw Her mai@W Stationery Oft by the Courier Press Leamington Spa, 1980. Publi by the Patent Office. 25 Southampton Buildiiigs. L WC2A l AY, from which copies rnay tte obtgin@& 1 i j i i 1 1